The present invention relates to a pulse frequency multiplier for multiplying an input pulse frequency using bipolar transistors.
Conventionally, various types of frequency multipliers which use bipolar transistors are known. For example, a simple circuit which is readily arranged as an integrated circuit is disclosed in Japanese Patent Publication (Kokoku) No. 56-45459 issued to E. Taira and assigned to Matsushita Denki Sangyo. As shown in FIG. 1, a triangular wave voltage B is generated by a constant current source 1 and a capacitor 2. The voltage B is pulsated by a voltage level switch 3. The pulse signal from the voltage level switch 3 is frequency-divided by a flip-flop 4 which then produces pulse signals A and A. A current control switch 5 is controlled in accordance with the pulse signal A, thereby controlling a period of the voltage B. The voltage B is also supplied to a differential amplifier 6 which then produces triangular wave signals B and B of opposite phases. The signals B and B are both supplied to differential amplifiers 7 and 8. The signal A is supplied to the differential amplifier 8 and the signal A is supplied to the differential amplifier 7. Output pulses C7 and C8 from the differential amplifiers 7 and 8 respectively are coupled to a buffer transistor 9, and a composite voltage is obtained.
However, in the frequency multiplier of the type described above, the triangular wave voltage is simply generated and multiplied. No method is described which receives and multiplies an arbitrary pulse signal. Furthermore, since the triangular wave voltage is generated by an open loop, a triangular wave voltage which is proportional to the magnitude of the input pulse cannot be produced, resulting in inconvenience. In other words, it is impossible to multiply the frequency of an input pulse.